This invention relates to a flexible disk drive for driving a flexible disk and, in particular, to a high-density flexible disk drive capable of driving a large-capacity flexible disk. This invention also relates to a large-capacity flexible disk to be inserted into the high-density flexible disk drive.
As well known, a flexible disk drive is a device for carrying out data recording and reproducing operations to and from a flexible disk inserted therein. In recent years, the flexible disk is more and more improved to have a greater capacity. Specifically, development is made of a large-capacity flexible disk having a storage capacity as large as 128 Mbytes in contrast with a normal-capacity flexible disk having a storage capacity between 1 Mbyte and 2 Mbytes. Following such development, the flexible disk drive is also improved to accept the large-capacity flexible disk for data recording and reproducing operations to and from the large-capacity flexible disk.
Throughout the present specification, a flexible disk drive capable of carrying out data recording and reproducing operations to and from the large-capacity flexible disk alone will be referred to as a high-density dedicated flexible disk drive. On the other hand, a flexible disk drive capable of carrying out data recording and reproducing operations to and from the normal-capacity flexible disk alone will be called a normal-density dedicated flexible disk drive. A flexible disk drive capable of carrying out data recording and reproducing operations to and from both the large-capacity and the normal-capacity flexible disks will be called a high-density/normal-density flexible disk drive. The high-density dedicated flexible disk drive and the high-density/normal-density flexible disk drive will collectively be called a high-density flexible disk drive.
The normal-density dedicated flexible disk drive and the high-density flexible disk drive are different in mechanism from each other in several respects, one of which will presently be described. In either flexible disk drive, a magnetic head is supported by a carriage which is driven by a drive unit to move in a predetermined radial direction with respect to the flexible disk inserted into the flexible disk drive. The difference resides in the structure of the drive unit. Specifically, the normal-density dedicated flexible disk drive uses a stepping motor as the drive unit. On the other hand, the high-density flexible disk drive uses a linear motor such as a voice coil motor (VCM) as the drive unit.
Now, description will be made in detail as regards the voice coil motor used as the drive unit in the high-density flexible disk drive. The voice coil motor comprises a voice coil arranged at a rear side of the carriage and wound around a drive shaft extending in parallel to the predetermined radial direction, and a magnetic circuit for producing a magnetic field in a direction intersecting that of an electric current flowing through the voice coil. With this structure, when the electric current is made to flow through the voice coil in a direction intersecting that of the magnetic field produced by the magnetic circuit, a drive force is generated in an extending direction of the drive shaft as a result of an interaction between the electric current and the magnetic field. By the use of the drive force, the voice coil motor makes the carriage move in the predetermined radial direction.
In the meanwhile, the large-capacity flexible disk generally has an external configuration identical with that of the normal-capacity flexible disk. Specifically, both of the large-capacity and the normal-capacity flexible disks have a flat rectangular shape of a width of 90 mm, a length of 94 mm, and a thickness of 3.3 mm in case of a 3.5-inch type.
It is therefore possible to insert the large-capacity flexible disk into the normal-density dedicated flexible disk drive. Even if the large-capacity flexible disk is erroneously inserted into the normal-density dedicated flexible disk drive, a data writing operation is impossible because a write protect function is activated in a circuit operation.
In such an event, however, the magnetic head of the normal-density dedicated flexible disk drive carries out a loading operation with the magnetic head brought into contact with a magnetic medium of the large-capacity flexible disk although the data writing operation is inhibited as described above. At this time, dust is unavoidably adhered onto the magnetic disk medium of the large-capacity flexible disk from the magnetic head. When the large-capacity flexible disk with the dust adhered to the magnetic disk medium is removed from the normal-density dedicated flexible disk drive and inserted into the high-density flexible disk drive, the magnetic head of the high-density flexible disk drive and the magnetic disk medium may possibly be damaged.
On the contrary, the normal-capacity flexible disk can be inserted into the high-density dedicated flexible disk drive. The high-density dedicated flexible disk drive can not judge whether or not a flexible disk inserted therein is the normal-capacity flexible disk or the large-capacity flexible disk until the flexible disk is accessed. When it is judged that the flexible disk is the normal-capacity flexible disk, the normal-capacity flexible disk must be removed from the high-density dedicated flexible disk drive.